A photograph on Cap sac (coming-of-age) ritual from the awarded collection.
The images depict a Dao ethnic minority "maturity ceremony" in the northern province of Lai Chau. This nine-day ritual marks the moment when a teenaged boy becomes a man.
"We came across the ceremony by chance during a business trip to Lai Chau," the Vietnam Pictorial magazine photojournalist said. "We had to ask for permission from the head of the village and the boys' families to take photos during the event."
Thien took more than 1,000 photos and chose the best nine to enter in the contest. All are original photos without any technical interference such as computer processing.
"I'm happy to have gotten the chance to witness and capture on film the most beautiful moments in local boys' lives," he said. "The ceremony confirms the role of local men in the community. It's a priceless custom of the group that needs to be handed down."
Thien beat more than 790 other photographers, who submitted more than 12,300 entries including 478 groups of photos.
Photographer Kieu Tan from the southern province of Dong Nai sent the most photos (328), followed by Hanoi photographer Hoang Minh (197), according to Nguyen Thang, the magazine's editor-in-chief and head of the contest organising board.
"This was the most comprehensive collection of photo contest entries ever in the country. It reflects the best images of the country's landscapes, people and cultural customs," said Nguyen Khanh, head of the jury.
In addition to the first prize, the jury awarded two second prizes, three third prizes and seven encouragement prizes.
The contest was co-organised by Vietnam Pictorial in co-ordination with the Vietnam Artistic Photographers Association to celebrate the 60th anniversary of the magazine.
More than 100 photos from this year's contest are on display at the Vietnam News Agency headquarters at 5 Ly Thuong Kiet street.
The exhibited photos will also be printed in the magazine's English, Chinese, Spanish and Lao print editions, and posted on the magazine's website in Vietnamese, English, French, Russian, Chinese, Japanese, Spanish, Lao and Khmer.